Refactor the backend folder structure

[WildBunnie]

Issue

Not related to an issue

Reason for this change

The folder structure did not follow a coherent pattern nor the best practices for the spring boot folder structure

Description of changes

Moved the backend from inside the "uasmartsignage" folder to the backend folder. Rename folders to be consistent. Changed the maven group id from deti.uas.uasmartsignage to pt.ua.deti.uasmartsignage

Description of how you validated changes

Ran the tests and the program locally

Checklist

• [x] I have tested my changes locally.
• [ ] I have updated the documentation to reflect my changes.
• [x] I have added/updated unit tests (if applicable).
• [x] My code adheres to the CONTRIBUTING GUIDE

[sonarcloud[bot]]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
No data about Coverage
No data about Duplication

See analysis details on SonarCloud

[sonarcloud[bot]]

Quality Gate failed

Failed conditions
1 Security Hotspot
42.4% Coverage on New Code (required ≥ 80%)

See analysis details on SonarCloud